Telephony users have long had to deal with a proliferation of user devices (sometimes referred to as ‘user equipment’ or ‘endpoints’) through which third parties may contact them. For example, a user might have a fixed-line (or ‘wireline’) telephony user device for use at home, a further fixed-line telephony user device for use in the office, and a mobile telephony user device for use whilst on the move. Each type of telephony device has associated advantages; whilst a mobile telephony device provides the user with mobility, a fixed-line telephony device typically provides more reliable and higher quality communications and no battery recharge concerns.
Users may also have a number of different access technologies available through which their user devices may conduct communications. For example, a user device may be equipped with a circuit-switched communication interface and one or more circuit-switched communication clients for conducting communications via suitable circuit-switched networks. Likewise, a user device may also/alternatively be equipped with a packet-switched communication interface and one or more packet-switched communication clients for communicating via suitable packet-switched networks.
A circuit-switched user device may comprise a fixed-line Plain Old Telephone Service (POTS) telephone equipped with a circuit-switched interface and communication client for conducting communications via a Public Switched Telephone Network (PSTN). A circuit-switched user device may comprise a mobile (or ‘cellular’) telephone equipped with a wireless circuit-switched interface and communication client for conducting communications via a cellular network such as a Global System for Mobile Communications (GSM) network or Code Division Multiple Access (CDMA) network.
More recently, packet-switched user devices have proliferated which may take the form of a fixed-line Internet Protocol (IP) telephone equipped with a fixed-line packet-switched interface and communication client for communicating via an Internet Protocol (IP) network, such as the internet or an IP Private Branch Exchange (IP-PBX). Similarly, a user may conduct communications via a personal computer (PC) equipped with a packet-switched communication client for conducting communications over the internet via a fixed-line internet connection. A mobile packet-switched user device may take the form of a portable computing device, such as a laptop or tablet, equipped with a wireless packet-switched interface and communication client for communicating via an IP network, such as the internet, using a Wi-Fi™ or Bluetooth™ compliant wireless access point. A packet-switched communication client may conduct communications according to an internet telephony protocol, commonly referred to as Voice over Internet Protocol (VoIP), with associated control protocols such as the Session Initiation Protocol (SIP) or H.323.
Increasingly, user devices are available that are equipped with multiple communication interfaces to facilitate communication via multiple access technologies. For example, a modern “smartphone” is typically equipped with a circuit-switched interface for communicating via a cellular telephone network and a packet switched interface for communicating via the internet. Commonly, a smartphone may be equipped with several packet-switched interfaces, for example, a short-range radio interface, e.g. Wi-Fi™ or Bluetooth™ compliant, and/or or via an interface for communication of packet data through a cellular network, such as 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), LTE-Advanced (LTE-A), High Speed Packet Access (HSPA), Wideband Code Division Multiple Access (W-CDMA) or Mobile WiMax etc. In such cases, a packet-switched communication client may also be deployed for conducting communications via one or more of the available wireless packet-switched interfaces. A suitable packet-switched communication client may be deployed on a user device prior to sale, or could be deployed subsequently through an application distribution portal such as the Apple™ App Store™ or Android™ Market etc.
To avoid confusing calling parties with identifiers such as telephone dialing numbers for each of the various communication clients of a user, a one-telephone dialing number telephony service allows the user to publish a single telephone dialing number on which they can be contacted. Thus, when the single telephone dialing number is called, all of the user's communication clients will ring, preferably simultaneously. The user is then able to answer the call at a user device and communication client of his choosing, via an access technology of his choosing.
When a plurality of communication clients is equipped on a single user device, the communication clients are said to be co-located. For example, a single user device may contain a cellular communication client and a VoIP communication client. With such a user device containing co-located communication clients, it is possible that communication sessions such as voice calls can be completed in a number of situations where a single communication client device would have no service available.
For example in remote areas where there is no Wi-Fi or mobile data connection available, a cellular communication client may still be able to complete calls. Conversely, in areas of weak cellular reception, such as inside a large building, a VoIP communication client (or ‘soft client’) may still be able to complete a call if there is an accessible Wi-Fi access point available. However, current systems provide a poor user experience in this area, when attempting to initiate an outgoing communication session, requiring the user to potentially fail to initiate a communication session setup attempt via one communication client before manually switching to another communication client to attempt to initiate setup of a communication session. The situation is often worse for incoming communication session setup requests, where the calling party has to manually try each of the other party's communication clients in turn in order to determine their reachability.
It would therefore be desirable to provide improved ways to communicate using devices with multiple co-located communication clients.